The present invention relates to a process for the radioactive decontamination of an oil more particularly applicable with regards to the decontamination of oils used in nuclear installations.
The, in nuclear installations, oils used in machines, such as e.g. primary pumps, can after a certain time be contaminated by radioactive elements. The activity level varies from to 3.7.multidot.10 .sup.6 to 3.multidot.7.multidot.10.sup.4 Bq/m.sup.3, as approximate figures the non-contamination threshold being set at 3.7.multidot.10.sup.3 Bq/m.sup.3. In oils used on primary pumps, the main contaminant is xenon 133, but the latter has a relatively short half-life (5.3 days) and after this time oils are at roughly the same activity level of approximately 3.7.multidot.10.sup.4 Bq/m.sup.3. Apart from xenon 133, the other radioelements liable to be found in contaminated oils are in particular manganese 54, cobalt 58, cobalt 60, niobium 95, iodine 131, cesium 134, cesium 137 and cerium 144.
The method presently used for getting rid of contaminated oils consists of burning them. This incineration produces on the one hand ash, which can be removed in storage drums, and on the other hand gaseous products which have to be treated. For this purpose, they are passed through so-called absolute filters, i.e. filters which hold back substantially all the dust and solid particles, even when in very fine form.
Although the disposal of the ash causes no particular problems, the treatment of large gas quantities requires large and therefore costly installations. In addition, it is common practice to make do with smaller installations, which only makes it possible to achieve small processing rates in the radioactive decontamination of oils.